DP losing server ID , and ''lost server''

Hi allI have a weird thing going on with one of my DP's , I have 2 connected all on fixed Ip's running latest sw (was doing the same on 3.51) , in the network window it is used , found and running however it has no server ID and on the actual DP it says lost server ,sometimes the server ID comes back and then goes away , I have swapped everything out and reloaded s ware etc , anyone seen this before ??? Im wondering if its the network card in the DP. this is all on a long running H4PC setup